tom-rhea-introduction to music technology

8/10/2019 Tom-Rhea-Introduction to Music Technology

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by Tom

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COLI.EeF () o' r ll '

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•

Introduction

Introduction:

MTO

0

landbotlk

. utYou

Should

ReadThis One

This booklet

is

designed

to

make your classroom experience

in

Berklee's

MTO I 0 Introduction to Music Technology course more productive and

more pleasant.

It

lightens your note-taking load, and makes it possible for

teacher and students

to

do what humans do best-interact.

Nothing takes the place of

learning by doing

and opportunities using

Berklee's unparalleled facilities are provided

in

this course

to

do

just

that.

Learning also occurs in the time-honored way of the musician-by being

shown.

The demonstrations in class will

be

much more vivid

i

you can

focus

on

them without furiously scribbling "notes" that you have

to

de-

code later

Obviously, this written material is not a substitute for classroom participa-

tion. Nor will it "teach" you things that you must do or be shown in order

to

learn. But it will provide a framework of tenus and concepts that sup-

port your understanding

of

the music technology that is around you. The

typography

of

this text also supports your review

of

the material for

exams, with words

in

bold that

summarize

important ideas.

This booklet answers some

of

the "what" questions about music technol-

ogy. Your classroom experience and hands-on opportunities will answer

some

of

the questions about "how." And

i

you persist, you may

come

to

see that "music technology" has

always

been with

us it

is not some

foreign idea unique to your time and this place. You will then begin

to

provide yourself with the tools that help you give personal answers

to

the

many "whys?" that have motivated the creative musical act through the

ages.

And,

as

always,

if

you discover something that gives meaning, increases

freedom, or brings joy share it with your friends

5



Sound Pro . es

=

There's an old riddle about sound that asks: if a tree falls in the fores

t

does it make a sound

if

nobody is there to hear it? The heated debate that

can arise depends on how you define sound. One dictionary tells us that

sound

is

mechanical radiant energy that is transmitted by longitudinal

pressure waves in a material medium, while another definition defines

sound as vibrations in air, water, etc. that stimulate the auditory nerves

and produce the sensation of hearing. You can find a definition

to

fit

either answer to the riddle, depending on whether trees fall

in

splendid

isolation or in your back yard while you're cooking barbecue. Is sound

energy that is transmitted even if nobody is listening, or is it the sensation

o

hearing which requires a listener?

Scientific instruments can sense, record, and report on vibrations of the

earth (seismic), or the air (sonic). No listener need be present for these

devices

to

prove that sound

as

energy that is transmitted occurs when a

tree falls.

f

several instruments report this sound you would expect

agreement among them, for well-designed scientific instruments provide

us

with objective information. That is, information that is directly measur-

able, real or actual, independent of the mind's interpretation. And you

aren t surprised to fmd that this kind of information is expressed using

numbers expressed on a scale people have agreed upon.

On the other hand you expect listeners to talk about sound using language

that is subjective affected by, or produced by the mind or state of mind.

Subjective information typically is not subject

to

being checked externally

or being verified by other persons. About the best you can

do

is to survey

a group of people to see i f there is any agreement about what they hear.

For centuries musicians have described sound subjectively, using words

like sharp, flat, loud, shrill. bright, dark. incisive. loud. soft. etc. Musicians

have recognized the general properties of musical sound: pitch, timbre

(tone color), loudness, and duration.

If

we think

of

duration

as

simply the

timing

of

loudness. it is simpler to say that musical sound has the subjec-

tive sound properties: pitch. timbre, and loudness. These properties are

quite real to us, and there is much agreement concerning how we hear

them. but they are subjective nevertheless. Subjective properties of sound

have to do with the sensation

o

hearing. Musicians recognize the interval

of an octave and respond in predictable ways to dynamic markings such as

ppp mf and ffJ but these sound properties rely on (subjective) human

judgment and musical experience

----------------------

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MTOJO Handbook



hapter

•

Sound Prope rries

Musicians have traditionally given little thought

O

the individu::ll

pro

er-

ties

of

sound-objective or subjective, because acoustic instruments gener-

ally don't offer independent control over sound properties. T:.e ph. _icai

characteristics of acoustic instruments dictate that control or-sound pro

tics is somewhat

integrated

For example, because of its

construction.

the

clarinet has a characteristic timbre (tone color) for each

of

Its ihree pi<ch

registers. It would be difficult to play high notes with me timbre rloun: lly

associated with the low register. The trumpet has a built-in

relation,hi

t

between timbre and loudness: soft sounds tend to be mellow and lou'::

sounds are brilliant. For thousands of years musical instrumems

naye

hJ."

this characteristic integration of control

of

the properties

of

sou,'lu.

You

just can't tear instruments made of metal and wood apan easily

t:

at

ow

independent control over sound properties. Historically. mu-ic:311: h:I"e

had little interest in the science of sound because so little eouid · .e

about

il

Electronic technology is changing our possibilities fo r olltrOllL'l : ur : .

and the concepts

we

have in making music. with electronic me2-':

we cart override some

of

the built-in tendencies

of aco ti

in.:mun nt.:--

we hope for artistic effect. For instance, screaming-loud

uumpe

C:1.

recorded and reduced to a low level in the final mix: In a.se. in

dent control

of

loudness and timbre can create a brilliant. ut "uie .

sound-overcoming the "natural" characteristics

of

the inst:rurni .lt.

-

this is what early composers

tried

to

achieve when they \\

.....

••

trumpet parts?

In fact, modern electronic musical instruments and rec rdin ue . _

:e- ,

,

maximize the segregation of sound properties.

Some

ynth.> ·ze

\ .

-

deal with sound properties individually at a mi ros opi

ley

1. Tn > i.: _

growing tendency to express sound properties numerical.ly. aI1u in

•

language of the

objective

sound properties:

frequency.

sp trum. Bye

shape, and

intensity.

Objective language has a clear meaning regardle-,,,,

language, culture, gender, etc. The re"

designers and others who understand thi langu ge i

-

f diffe. '

wish to shape and control sound. On the oth r h nd. th'

ear-a SUbjective organ to be sure-has the 1 t t

rd

n In : i

Music is for

people-nol

machines The m r , u .

I

\\

:1 t

-

and subjective sound propenies.

the

Ie u: th : . r

diction will seem.

•

•

..• , 1''-

-



Chapter 1

•

Sound Properties

Pitch-

MTOJO

Handbook

You tune up before playing by matching the pitch of your instrument

to

some tuning reference such as A above middle

t

so happens that th e

pitch of the musical note known as A above middle C has varied wide ly

over the centuries in different countries. Only in this century has A-440

been accepted to standardize the tuning of modern instruments and the

pitch of our musical scale. But what does A-440 mean? The number

440 represents a frequency standard, meaning that a sound that repea

ts

its vibration 440 times per second will occupy the

A

above middle C

position on our musical scale. Note the use of numbers and the standard-

ized time unit se ond

to

describe this objective property

of

sound. We

judge the

pitch-we

measure its frequency.

Freque1ZC)

1 _

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Tif1U

Time

Lower

Frequency

lflPtr

Frequency

.1 -

Let's see how pitch and frequency relate.

We

hear pitch as the highness or

lowness of a sound. The piccolo plays high pitches; the tuba plays low

pitches. Our perception

of

pitch is complex, but depends mostly on how

frequently and regularly sound pressure waves strike our ears. Many

children

make

a motor for their bicycle

by

attaching a piece

of

card-

board so the spokes strike it regularly. TIle faster the wheel turns, the

higher the pitch of the sound caused by the spokes striking the cardboard.

That's because the individual spoke sounds are heard more frequently-

there are more repetitions per second. Pitched sound is a periodic phe-

nomenon in which a particular vibration pattern repeats regularly. Fre-

quency is defined as the

number

of times a given pattern repeats in a unit

of time-usually a second. Frequency is expressed numericaUy in ertz

(abbreviated Hz), or in outmoded tell lS

cycles per second abbreviated

cps .

The modern pitch standard produces an A above middle C with a

•

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JJ



Chaptu . SOllnd Properties

•

frequency of 440 Hz. Although the correspondence between frequency and

what we perceive as pitch

is

not perfect, a higher frequency is generally

heard as a higher pitch.

For

the scientist who measures frequency

in

Hertz, an octave is defined as

a 2: J ratio. That is, the octave above the note A at 440Hz is twice that

number, or

880 Hz. The octave above the note A

at

7,040 Hz is therefore

14,080 Hz. But the musician judges an octave or any other musical inter-

val by ear. And research has shown that the pitches musicians judge

to

bc

the interval of an octave do

not

always have a

2:

I ratio in frequency. We

tend

to

judge the extreme highs and lows of the perceptible pitch span

differently than the middle portion. We tend

to

want

to

stretch the high

frequencies higher, and the low frequencies lower

to

satisfy our musical

sense of pitch. Because of human anatomy your ear/brain perceives pitch

on a nonlinear, or

curved

response

to

the frequencies heard. Your ear

doesn't operate on the predictable linear, or straight line of a

2:

1 frequency

ratio for the scientist 's octave. And to make things worse, not all musi-

cians perceive pitch on the same curve

Timhre-Waveshape/Spectrnm

f everyone in the group plays the same note A-440 when tuning, what is

it that lets us tell one instrument from another? Why does each instrument

have a distinctive tone color even when playing the "same note?" It s easy

to tell one class

of

musical sound from another

by

how each sound starts

and ends. Whether a sound

is

bowed, blown, struck, etc. helps you judge

what kind of instrument is involved. This transient behavior involves the

attack and release, or how a sound

begins

and

ends.

and affects how we

tell which instrument is playing.

Also, if you view a steady tone made by a musical instrument on a scien-

tific instrument called an oscilloscope you see a distinctive waveshape.

This waveshape appears as a single line on the oscilloscope, a device that

can dynamically graph sound pressure level (SPL) as it changes in timc.

Since waveshape

is

a representation of sound in time, this depiction

is

known

as

the time domain. Time

is

depictcd along the horizontal aus.

and the amplitude. or size of the waveshape

is

shown on the vertical axis.

If the wavcshape is audible you perccive its amplitude as loudness. In the

time domain it is easy to idcntify classic waveshapcs such as the sawtooth,

square, triangular, becausc each shape suggests its name.

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hapter

1 .

Sound Properties

Waveform

s· Time omaitl epresentation

Time ' ..

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Saw looih

Square

Triangle

With a few exceptions, different waveshapes are heard

as

different tim-

bres. Most acoustic instruments have a distinctive waveshape that helps us

identify that instrument's unique timbre, or tone color. If an elec trical

signal generated by a sampler or synthesizer has the same waveshape as a

sound created by a traditional instrument (other factors such as transient

behavior considered) their sounds will be similar. Of course,

just

because

you can produce waveshapes of acoustic instruments doesn t mean you

can perform like people who have devoted a lifetime

to

the study

of

those

instruments

Looking at a waveshape is not necessarily the best way

to

know what

sound it will make. There is another way of representing sound graphi-

cally, the frequency domain. The differences you hear among various

static, or steady-state musical waveshapes are due to differences in their

spectra (plural). The spectrum (singular)

of

a particular waveshape

comprises a collection

of simple components, each of which is called a

pal

tial. Each partial is a sine wave having a unique frequency (hence

frequency domain) within that particular spectrum. A sine wave is a

representation

of

simple hallllOruc motion (abbreviated

SHM

) which can

be derived from circular motion, and illustrated by the pendulum

of

a

clock. A sine wave is a "pure" sound that cannot be simplified (it

isn t

a

collection

of

partials-i t is a partial). The closest sounds we have

to

illus-

trate a sine wave are a tuning fork tone (especially when aided by a reso-

nating box), singing

00

softly in falsetto, or the tone produced by blow-

ing across the opening

of

a bottle. A spectrum, or

frequency

domain

representation of a sound looks like a bar graph, or histogram. Each

partial

is

represented individually as a single vertical line on the hori-

zontal axis indicating its frequency. The height of an individual line

represents the strength

of

that partial: the

amplitude of

a partial

is

repre-

sented on the vertical axis.

-------------------------------- _.------_

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1 Handbook

•

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Sound Properties

14

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al

monic Number

Frequency

OTTUlin Representation

Harmonics and Nonharmonics

A periodic, or pitched sound in the world of music is usually not a simple

sine wave, it is a complex waveshape.

The

sound of a complex waveshape

is the result

of

the simultaneous vibrations of its several partials.

Many

complex waveshapes consist

of

a

first

partial called the fundamental.

and other partials

of

higher frequency and smaller amplitude. When thc

frequencies of these upper partials are whole number multiples of the

frequency

of

the fundamental, the partials are called

harmonics.

For

instance, a complex waveshape with a fundamental frequency of

100

Hz

might be composed

of

simple sounds (sine waves,

or

partials) having the

frequencies 100 Hz, 200 Hz, 300 Hz,

400

Hz. and so forth.

These

frequen-

cies are whole number

multiples

of the fundamental frequency 100Hz.

and are therefore harmonic. Whole numbers are integers.

and

all the

partials of a periodic, or pitched sound are harmonic. meaning the partials

have an

integral

relationship to the fundamental. Upper partials that are

harmonic tend to reinforce our perception of the fundamental frequency as

the pitch we identify.

The

presence and relative strengths of halIllonies thc

harmonic

spectrum accounts

in part for

our

perception

of

the timbre,

or

distinctive tone color of many musical instruments.

What if a partial is nonintegral: not a whole num er mlllTiple of the

fundamental? For instance. in the collection of partials: 100 Hz. 215 H7.

300

Hz, 400 Hz. 550 Hz the partials tuned to 215 Hz and 550 Hz arc

or

whole number multiples

of

the fundamental. Each of these partial is a

nonharmonic (sometimes called inhallllonic). A bell sound. a so-called

clangorous sound, usually has several nonharmonics in spectrum.

Sometimes there is no clear fundamental frequency in a clangorous sound.

and partials typically exhibit nonintegral relationships. If there is a mn

dom distribution

of

partials over the entire auditory rang.:, we hear noise .

whIch sounds like the static between stations on FM radio

O

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.

Chapur 1 - SoU lt1

Loudness-Intensity/Anlplitude

MTOJO andbook

If you look at a guitar string as it vibrates, it is apparent that the distance

that the string moves is related to how loud the sound is. The amplitude

or size

of

the vibrations, and the objective sound property

of

intensjty are

obviously related

to

the subjective sound property loudness. But it is

difficult to measure intensity directly outside the laboratory,

so

we mea-

sure sound intensity indirecLly using devices like a sound pressure (

SPL

)

meter using the decibel (dB ) scale. f we view a static audio waveshape on

the oscilloscope

we

can measure the signal

amplitude

(usually expressed

in the electrical unit

of

volts) on the vertical axis, and this also relates 0

the loudness that we hear. Using either device, we are

nOt

measuring

intensity directly, but an electrical signal that represents intensity. \Ve

often say that an electrical signal has a certain level, another name thal

indicates size.

Amplitude

Time -

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Smalkr

Ampf lude

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Of all the sound properties, loudness s the least well-behaved wheo we try

to

make it fit an objective property like intensity or amplitude. Imagine

that you listen to a quiet but audible sine wave whose amplitude remains

unchanged. You adjust its frequency over the tOtal span

of

human hearing.

What happens to its loudness as you change the frequency? You won t

hear the sine wave equally well

a1

every frequency. Loudness. which we

perceive subjectively, varies even though the objective signal amplitude

does not. In fact it would sound quite loud at 3.000 Hz 3 kiloHertz. or 3

kHz) and might not be audible at all at 30 Hz or at

15.000

Hz. If you

graphed your ear s response you would see another curve, indicating a

nonlinear response to a sine wave whose amplitude remains the same as its

frequency is changed. On the other hand a very loud sine wave with a

fixed amplitude sounds at about the same loudness at low. mid. and high

frequencies.

5



hapraJ • Sound

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6

Iffact,

there are several sets

of equal

loudness

curves

for sine

waves

that

illustrate this experiment, the earliest due

to Fletcher and Munson

These

curves graphically show that the ear is more linear, or "flat" in its response

at very high levels, and extremely nonlinear at lower levels. But

you ve

probably had a vivid example

of

the ear s nonlinearity regarding intensity/

loudness if you simply recall it: when the phone rings and you tum down

your stereo, what changes about the music? The lowest bass and highest

treble seem to disappear when you play music at a low level. This isn t a

deficiency of your stereo-it's caused by the nonlinear response of your

ears. Most stereo amplifiers have a so-called "contour" or "emphasis"

switch that electronically boosts lows and highs;

it s

use will "flatten out"'

the ear's response when playing at low levels and make the tonal balance

sound better. (Don't use it when playing at high levels-the ear doesn t

need it, and your neighbors probably don t either.) Try playing the same

passage on your stereo at different levels

to

demonstrate the ear s fre-

quency/loudness response

to

yourself

120 -

,-:

100 -

80

6

40

20

o

20

Hz

•

100

liz

lk Hz

MlNIMUM AUDIBLE FIELD

Threshold

of Hearing)

Equal Loudness

Co1/tOllrs

Robinson Dadson)

5kHz

10k Hz

/.U OIO Handlx>Qk



hapter1 ound

ropmlu

As we see. thl century' s music technology has some specialized teuIlS

and language. and we can better deal with this technology

i

we are famil-

iar with the e tCIIIlS In fact, there are many specialized tellBS within the

field

o

mU,ic. For instance. words like "nut" and "frog" and "bridge"

conjure up specific images for a nonmusician, but have a very different

meaning to a violinist

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•

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tom-rhea-introduction to music technology

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